Quantitative Predictions of Phase Behavior and Mass Transfer for Complex Mixed Wastes

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9805376CeliaMany contaminated sites involve non-aqueous-phase liquid (NAPL) pollutants that are complex mixtures of organic compounds. Current methods for describing NAPL contaminants in subsurface systems do not adequately account for spatial and temporal variations in contaminant compositions. An often-overlooked but important consideration is that NAPLs often contain compound that is solids in their pure forms at ambient temperatures, and which may solidify as the NAPL composition changes. This phenomenon may have a significant impact on the long-term fate of some complex-mixture NAPLs in the subsurface environment, with associated implications for risk assessment and decisions on clean-up actions. This project couples the thermodynamics of multicomponent phase equilibria with pore-scale computational models to investigate the fate of complex, mixed-waste NAPLs in subsurface environments. The major objectives are: (1) Perform laboratory experiments to investigate phase behavior, mass transfer and NAPL solidification at the pore scale and column scale. (2) Develop a compositional pore-scale numerical model to simulate fluid flow, behavior, and mass transfer for multicomponent contaminants in multi-phase porous media. (3) Perform risk assessment calculations using the laboratory and computational results to estimate long-term risks associated with complex-mixture NAPLs, and the effects of solidification of NAPL components. This projects focuses on NAPLs containing polycyclic aromatic hydrocarbons (PAHs), because of their importance as environmental contaminants, their complex multicomponent nature which necessitates a compositional approach, and the importance of potential phase transformations. To maximize inference ability in experimental investigations, a novel laboratory procedure is used which involves synthetic PAH-NAPLs to serve as representative yet well-characterized surrogates for environments contaminants.